Method for producing biohydrocarbons

ABSTRACT

The present invention relates to a method of producing biohydrocarbons which includes providing an isomeric raw material obtained from a bio-renewable feedstock, such as by deoxygenation, hydrodeoxygenation, hydrotreatment or hydrocracking, and containing at least 65 wt. % iso-paraffins, and thermally cracking the isomeric raw material to produce biohydrocarbons at a temperature (coil outlet temperature) of at most 825° C. The biohydrocarbons can further be polymerized to obtain bio-polymers such as polyolefins, polypropylene, polyethylene or copolymers such as polyethylene terephthalate.

TECHNICAL FIELD

The present invention relates to a method of producing biohydrocarbons.Further, the invention relates to biohydrocarbons obtainable by themethods of the invention and to a method of producing polymers.

BACKGROUND OF THE INVENTION

Production of biohydrocarbons from biomass is of increasing interestssince they are produced from a sustainable source of organic compounds.Such hydrocarbons are valuable in the chemical industry as basematerials for several processes, in particular as monomers or monomerprecursors in polymer chemistry.

Biopolymers are of great worldwide interest as they could give asustainable alternative to traditional fossil based polymers (e.g. PE,PP, PET, ABS). However, finding a biopolymer with properties which arecomparable to those of traditional polymers is very challenging. So far,large scale applications have been created only for polylactic acid(PLA). Replacing traditional polymers is not easy, as their productproperties are rather unique, the processing of the polymers is highlydeveloped and the processing machinery cannot be easily applied to novelpolymers as such.

US 2012/0053379 A1 discloses a method of producing biohydrocarbons usingcatalytic deoxygenation of tall oil components and steam cracking aliquid fraction derived from the deoxygenation step.

SUMMARY OF INVENTION

The present invention was made in view of the above-mentioned problemsand it is an object of the present invention to provide an improvedprocess for producing bio-renewable materials (biohydrocarbons) offeringa wide range of applications.

In brief, the present invention relates to one or more of the followingitems:

1. A method for producing biohydrocarbons, the method comprising:

a step of providing an isomeric raw material obtained from abio-renewable feedstock and containing at least 65 wt.-% iso-paraffins,and

a cracking step of thermally cracking the isomeric raw material toproduce biohydrocarbons,

wherein the thermal cracking in the cracking step is conducted at atemperature (coil outlet temperature COT) of at most 825° C.

2. The method according to item 1, wherein the isomeric raw materialcontains at least 68 wt.-%, preferably at least 70 wt.-%, morepreferably at least 75 wt.-%, more preferably at least 80 wt.-%, morepreferably at least 85 wt.-%, more preferably at least 90 wt.-%iso-paraffins.

3. The method according to item 1 or 2, wherein the thermal cracking inthe cracking step is conducted at a temperature (coil outlet temperatureCOT) of at most 820° C., preferably at most 810° C., preferably at most800° C., at most 790° C., or at most 780° C.

4. The method according to any one of the preceding items, wherein thethermal cracking in the cracking step is conducted at a temperature(coil outlet temperature COT) of at least 700° C., preferably at least720° C., at least 740° C., at least 750° C., or at least 760° C.

5. The method for producing biohydrocarbons according to any one of thepreceding items, wherein the step of providing the isomeric raw materialcomprises a preparation step of preparing a hydrocarbon raw materialfrom the bio-renewable feedstock, and optionally an isomerization stepof subjecting at least straight chain hydrocarbons in the hydrocarbonraw material to an isomerization treatment to prepare the isomeric rawmaterial.

6. The method according to item 5, wherein the preparation stepcomprises a step of deoxygenating the bio-renewable feedstock.

7. The method according to item 6, wherein the step of deoxygenating thebio-renewable feedstock is a hydrotreatment step.

8. The method according to item 6 or 7, wherein the step ofdeoxygenating the bio-renewable feedstock is a hydrodeoxygenation step.

9. The method according to any one of items 5 to 8, wherein thepreparation step comprises a step of hydrocracking hydrocarbons in thehydrocarbon raw material.

10. The method according to any one of the preceding items, wherein thebio-renewable feedstock comprises at least one of vegetable oil,vegetable fat, animal oil and animal fat and is subjected tohydrotreatment before the cracking step.

11. The method according to any one of the preceding items, wherein theisomeric raw material comprises at least one of a diesel range fractionand a naphtha range fraction and at least the diesel range fractionand/or the naphtha range fraction is subjected to thermal cracking.

12. The method according to item 11, wherein only the diesel rangefraction and/or the naphtha range fraction, preferably only the dieselrange fraction, is subjected to thermal cracking.

13. The method according to any one of the preceding items, wherein theisomeric raw material is preferably selected from one of fractions A andB, wherein

Fraction A comprises more than 50 wt.-%, preferably 75 wt.-% or more,more preferably 90 wt.-% or more of C10-C20 hydrocarbons (based on theorganic components), the content of even-numbered hydrocarbons in theC10-C20 range (i.e. C10, C12, C14, C16, C18 and C20) being preferablymore than 50 wt.-%, and the fraction A containing 1.0 wt.-% or less,preferably 0.5 wt.-% or less, more preferably 0.2 wt.-% or lessaromatics, and less than 2.0, preferably 1.0 wt.-% or less, morepreferably 0.5 wt.-% or less of olefins, and

Fraction B comprises more than 50 wt.-%, preferably 75 wt.-% or more,more preferably 90 wt.-% or more of C5-C10 hydrocarbons (based on theorganic components), and the fraction B containing 1.0 wt.-% or less,preferably 0.5 wt.-% or less, more preferably 0.2 wt.-% or lessaromatics, and less than 2.0, preferably 1.0 wt.-% or less, morepreferably 0.5 wt.-% or less of olefins.

14. The method according to any one of the preceding items, wherein theisomeric raw material contains at least 70 wt.-% iso-paraffins.

15. The method according to any one of the preceding items, wherein theisomeric raw material contains at most 1 wt.-% oxygen based on allelements constituting the isomeric raw material, as determined byelemental analysis.

16. The method according to any one of the preceding items, wherein thethermal cracking in the cracking step comprises steam cracking.

17. The method according to item 16, wherein the steam cracking isperformed at a flow rate ratio between water and the isomeric rawmaterial (H₂O flow rate [kg/h]/iso-HC flow rate [kg/h]) of 0.05 to 1.20.

18. The method according item 17, wherein the flow rate ratio betweenwater and the isomeric raw material is at least 0.10, preferably atleast 0.20, more preferably at least 0.25, even more preferably at least0.30.

19. The method according to item 16 or 17, wherein the flow rate ratiobetween water and the isomeric raw material is at most 1.00, preferablyat most 0.80, more preferably at most 0.70, at most 0.60, or at most0.50.

20. The method according to any one of the preceding items, wherein thebiohydrocarbons comprise at least 15 wt.-% propene.

21. The method according to any one of the preceding items, wherein thebiohydrocarbons comprise at least 16 wt.-%, preferably at least 17wt.-%, preferably at least 18 wt.-%, preferably at least 19 wt.-%,preferably at least 20 wt.-%, preferably at least 21 wt.-% propene.

22. A method for producing biohydrocarbons, the method comprising:

a preparation step of preparing a hydrocarbon raw material from abio-renewable feedstock,

an isomerization step of subjecting at least straight chain hydrocarbonsin the hydrocarbon raw material to an isomerization treatment to preparean isomeric raw material, and

a cracking step of thermally cracking the isomeric raw material toproduce biohydrocarbons, wherein the thermal cracking in the crackingstep is conducted at a temperature (coil outlet temperature COT) of atmost 825° C.

23. The method according to item 22, wherein the isomeric raw materialcontains at least 65 wt.-%, preferably at least 68 wt.-% iso-paraffins.

24. The method according to item 22 or 23, wherein the isomeric rawmaterial contains at least 70 wt.-%, preferably at least 75 wt.-%,preferably at least 80 wt.-%, more preferably at least 85 wt.-%, mostpreferably at least 90 wt.-% iso-paraffins.

The additional features of items 2 to 21 are applicable to the method ofany one of items 22 to 24 as well.

25. A method of producing a polymer, comprising producingbiohydrocarbons according to the method of any one of items 1 to 24,optionally purifying and/or chemically modifying at least a part of thebiohydrocarbons to provide biomonomers, and polymerizing the biomonomersto obtain a polymer.

26. The method according to item 25, wherein the polymer is apolyolefin, such as polypropylene and polyethylene, or a copolymercomprising propylene units and/or polyethylene units, such aspolyethylene terephthalate (PET), or a derivative thereof.

27. The method according to item 25 or 26, wherein the method employs atleast 50 wt.-%, preferably at least 80 wt.-%, more preferably at least90 wt.-%, more preferably at least 95 wt.-%, more preferably more than99 wt.-%, even more preferably 100 wt.-% of monomers derived frombio-renewable raw materials, relative to all monomers constituting thepolymer.

28. The method according to any one of items 25 to 27, wherein themethod further comprises forming an article, such as a film, beads, or amolded article from the polymer.

29. A mixture of biohydrocarbons obtainable by the method according toany one of items 1 to 24.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a laboratory scale steam cracking setup used in theExamples of the invention.

FIG. 2 shows a GC×GC set-up (cf. Beens, J.; Brinkman, U. A. T.,Comprehensive two-dimensional gas chromatography-a powerful andversatile technique. Analyst 2005, 130, (2), 123-127).

FIG. 3 shows a GC×GC output in a 2D (grayscale) plot, in a 2D contourplot and in a 3D plot, respectively (cf. Adahchour, M.; Beens, J.;Vreuls, R. J. J.; Brinkman, U. A. T., Recent developments incomprehensive two-dimensional gas chromatography (GC×GC) II. Modulationand detection. Trends in Analytical Chemistry 2006, 25, (6), 540-553).

FIG. 4 shows reference components for GC×GC analysis

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method of producing biohydrocarbons,the method comprising thermally cracking an iso-paraffin composition (inthe following: isomeric raw material) having a high content ofiso-paraffins. The isomeric raw material may be obtained byisomerization of a hydrocarbon raw material derived from a bio-renewablefeedstock.

In general, the present invention relates to a method of producinghydrocarbons derived from a bio-renewable feedstock (biohydrocarbons),thus contributing to environmental sustainability of industry dependingon petrochemical products, specifically polymer industry and fuelindustry. The product resulting from the method of the inventionpreferably has a high content of polypropylene.

The present invention provides a method for producing biohydrocarbons,the method comprising a step of providing an isomeric raw materialhaving a high iso-paraffin content, and a cracking step of thermallycracking the isomeric raw material at relatively low temperature.

The isomeric raw material preferably contains at least 65 wt.-%, morepreferably at least 68 wt.-%, further preferably at least 70 wt.-%, atleast 75 wt.-%, at least 80 wt.-%, at least 85 wt.-%, or at least 90wt.-% iso-paraffins.

The higher the amount of iso-paraffins, the higher the propylene yieldin the thermal cracking step, which is of particular value in polymerchemistry. Therefore, it is particularly preferable that the isomericraw material preferably contains at least 70 wt.-% iso-paraffins.

Using the method of the present invention, it is possible to convert abio-renewable feedstock into a petrochemical raw material containing ahigh amount of propylene (propene) as well as ethylene (ethene) and BTX(benzene, toluene, xylenes) which are particularly suited for furtherproduction of polymer materials. As a matter of course, other productcomponents are useful as well, e.g. as solvents, binders, modifiers orin fuel industry.

In the present invention, iso-paraffins are branched alkanes having acarbon number of preferably at most C24, while n-paraffins arestraight-chain alkanes having a carbon number of preferably at most C26.

The specific method steps employed in the present invention and theintermediate and end products resulting from these method steps will beexplained in more detail below. However, the present invention is notlimited to the below preferred embodiments.

Bio-Renewable Feedstock

In the present invention, the bio-renewable feedstock may be derivedfrom any bio-renewable source, such as plants or animals, includingfungi, yeast, algae and bacteria, wherein the plants and the microbialsource may be gene-manipulated. In particular, the bio-renewablefeedstock preferably may comprise fat, such as vegetable fat or animalfat, oil (in particular fatty oil), such as vegetable oil or animal oil,or any other feedstock that can be subjected to biomass gasification orBTL (biomass to liquid) methods. The bio-renewable feedstock may besubjected to an optional pre-treatment before preparation of ahydrocarbon raw material or of the isomeric raw material. Suchpre-treatment may comprise purification and/or chemical modification,such as saponification or transesterification. If the bio-renewable rawmaterial is a solid material, it is useful to chemically modify thematerial so as to derive a liquid bio-renewable feedstock.

Preferably, the bio-renewable feedstock comprises at least one ofvegetable oil, vegetable fat, animal oil and animal fat. These materialsare preferred, since they allow providing a feedstock having apredictable composition which can be adjusted as needed by appropriateselection and/or blending of the natural oil(s) or fat(s).

Isomeric Raw Material

The isomeric raw material of the present invention contains at least 65wt.-%, more preferably at least 68 wt.-%, further preferably at least 70wt.-%, or at least 75 wt.-% iso-paraffins. Further the content may be atleast 80 wt.-%, at least 85 wt.-%, or at least 90 wt.-% iso-paraffins.The higher the iso-paraffin content of the isomeric raw material, thehigher the amount of propylene resulting from thermal cracking (steamcracking). In the present invention, the content of iso-paraffins in theisomeric raw material is determined relative to all organic materialwhich is fed to the cracker (i.e. relative to all organic material inthe isomeric raw material). The content of iso-paraffins may bedetermined using GC×GC analysis, as explained in the Examples, or by anyother suitable method.

In general, any isomeric raw material as defined above can be used inthe present invention. Nevertheless, two specific iso-paraffin fractions(A and B) are to be mentioned, which provide particularly desirableproduct distribution and which are favorable in view of HSE (health,environment, safety).

Fraction A comprises more than 50 wt.-%, preferably 75 wt.-% or more,more preferably 90 wt.-% or more of C10-C20 hydrocarbons (based on theorganic components). The content of even-numbered hydrocarbons in theC10-C20 range (i.e. C10, C12, C14, C16, C18 and C20) is preferably morethan 50 wt.-%. The fraction A contains 1.0 wt.-% or less, preferably 0.5wt.-% or less, more preferably 0.2 wt.-% or less aromatics, and lessthan 2.0, preferably 1.0 wt.-% or less, more preferably 0.5 wt.-% orless of olefins.

Fraction B comprises more than 50 wt.-%, preferably 75 wt.-% or more,more preferably 90 wt.-% or more of C5-C10 hydrocarbons (based on theorganic components). The fraction B contains 1.0 wt.-% or less,preferably 0.5 wt.-% or less, more preferably 0.2 wt.-% or lessaromatics, and less than 2.0, preferably 1.0 wt.-% or less, morepreferably 0.5 wt.-% or less of olefins.

In any case, the isomeric raw material preferably contains at most 1wt.-% oxygen based on all elements constituting the isomeric rawmaterial, as determined by elemental analysis. A low oxygen content ofthe isomeric raw material (i.e. the organic material fed to thermalcracking) allows carrying out the cracking in a more controlled manner,thus resulting in a more favorable product distribution.

Hydrocarbon Raw Material and Preparation Step

The isomeric raw material of the present invention may be provided byisomerizing a hydrocarbon raw material obtained from the bio-renewablefeedstock.

Generally, the hydrocarbon raw material may be produced from thebio-renewable feedstock using any known method. Specific examples of amethod for producing the hydrocarbon raw material are provided in theEuropean Patent application EP 1741768 A1. It is also possible to employanother BTL method, such as biomass gasification followed by aFischer-Tropsch method.

A preparation step of preparing the hydrocarbon raw material preferablycomprises a step of deoxygenating the bio-renewable feedstock, sincemost bio-renewable raw materials have a high content of oxygen which isunsuited for the thermal cracking (preferably steam cracking) step ofthe present invention. That is, although steam cracking ofoxygen-containing bio-renewable raw material was reported before, theproduct distribution is undesirable and unpredictable. The presentinvention, on the other hand, allows producing a biohydrocarboncomposition which can be readily integrated into the value-added chainof conventional petrochemistry. In the present invention, thedeoxygenating method is not particularly limited and any suitable methodmay be employed. Suitable methods are, for example, hydrotreating, suchas catalytic hydrodeoxygenation (catalytic HDO), and catalytic cracking(CC) or a combination of both. Other suitable methods includedecarboxylation/decarbonylation reactions either alone or In combinationwith hydrotreating.

Preferably, the step of deoxygenating the bio-renewable feedstock is ahydrotreatment step, preferably a hydrodeoxygenation (HDO) step whichpreferably uses a HDO catalyst. This is the most common way of removingoxygen and was extensively studied and optimized. However, the presentinvention is not limited thereto.

As the HDO catalyst, a hydrogenation metal supported on a carrier may beused. Examples include a HDO catalyst comprising a hydrogenation metalselected from a group consisting of Pd, Pt, Ni, Co, Mo, Ru, Rh, W or acombination of these. Alumina or silica is suited as a carrier, amongothers. The hydrodeoxygenation step may for example be conducted at atemperature of 100-500° C. and at a pressure of 10-150 bar (absolute).

The step of preparing the hydrocarbon raw material may comprise a stepof hydrocracking hydrocarbons in the hydrocarbon raw material. Thus, thechain length of the hydrocarbon raw material can be adjusted and theproduct distribution of the biohydrocarbons can be indirectlycontrolled.

The hydrotreatment step and an isomerization step may be conducted inthe same reactor.

Water and light gases may be separated from the hydrotreated orhydrocracked composition and/or from the isomeric raw material with anyconventional means, such as distillation, before thermal cracking. Afteror along with removal of water and light gases, the composition may befractionated to one or more fractions, each of which may be used as theisomeric raw material in the thermal cracking step or as the hydrocarbonraw material in the isomerization step. The fractionation may beconducted by any conventional means, such as distillation. Purificationand/or fractionation allows better control of product properties.

In the present invention, it is preferable that a bio-renewablefeedstock comprising at least one of vegetable oil, vegetable fat,animal oil and animal fat is subjected to hydrotreatment andisomerization to prepare an isomeric raw material comprising at leastone of a diesel range fraction (boiling point: 180-360° C.) and anaphtha range fraction (boiling point: 30-180° C.) and at least thediesel range fraction and/or the naphtha range fraction is thensubjected to thermal cracking (steam cracking). Preferably, only thediesel range fraction, only the naphtha range fraction or only a mixtureof the diesel range fraction and the naphtha range fraction is subjectedto thermal cracking. Most preferably, the diesel range fraction issubjected to thermal cracking. Using these fractions and in particularsuch fractions derived from oil and/or fat allows good control of thecomposition of the isomeric raw material and thus of the biohydrocarbonsproduced by the method of the present invention.

Isomerization Step

The isomeric raw material of the present invention may be provided byisomerizing a hydrocarbon raw material as described above. In theisomerization step, isomerization is carried out which causes branchingof the hydrocarbon chain and results in improved performance of theproduct oil at low temperatures. Usually, isomerization producespredominantly methyl branches. The severity of isomerization conditionsand choice of catalyst controls the amount of methyl branches formed andtheir distance from each other and thus influences the productdistribution obtained after thermal cracking.

The isomerization step preferably comprises subjecting at least a partof the straight chain alkanes in the hydrocarbon raw material to anisomerization treatment to prepare the isomeric raw material. Thestraight chain alkanes may be separated from the remainder of thehydrocarbon raw material, subjected to isomerization treatment and thenoptionally re-unified with the remainder of the hydrocarbon rawmaterial. Alternatively, all of the hydrocarbon raw material may besubjected to isomerization treatment. The isomerization treatment is notparticularly limited and is preferably a catalytic isomerizationtreatment.

It is preferred that only a part of the hydrocarbon raw material issubjected to an isomerization step, preferably the part of thehydrocarbon raw material corresponding to the heavy fraction boiling ator above a temperature of 300° C. In this case, the isomerization stepmay preferably be combined with a catalytic cracking step. The highboiling point part of the hydrocarbon raw material, after optionalcatalytic cracking, results mainly in a diesel range fraction afterisomerization, leading to improved product distribution.

The isomerization step may be carried out in the presence anisomerization catalyst and optionally in the presence of hydrogen.Suitable isomerisation catalysts contain a molecular sieve and/or ametal selected from Group VIII of the Periodic Table and optionally acarrier. Preferably, the isomerization catalyst contains SAPO-11 orSAPO-41 or ZSM-22 or ZSM-23 or fernerite and Pt, Pd or Ni and Al₂O₃ orSiO₂. Typical isomerization catalysts are, for example,Pt/SAPO-11/Al₂O₃, Pt/ZSM-22/Al₂O₃, Pt/ZSM-23/Al₂O₃ and Pt/SAPO-11/SiO₂.The catalysts may be used alone or in combination. The presence ofhydrogen is particularly preferable to reduce catalyst deactivation.Particularly preferable, the isomerization catalyst may be a noble metalbifunctional catalyst, such as Pt-SAPO and/or Pt-ZSM-catalyst, which isused in combination with hydrogen.

The isomerization step may for example be conducted at a temperature of200-500° C., preferably 280-400° C., and at a pressure of 20-150 bar,preferably 30-100 bar (absolute).

The isomerization step may comprise further intermediate steps such as apurification step and a fractionation step.

Incidentally, the isomerization step of the present invention is a stepwhich predominantly serves to isomerize the hydrocarbon raw materialcomposition. That is, while most thermal or catalytic conversions (suchas HDO) result in a minor degree of isomerization (usually less than 5wt.-%), the isomerization step which may be employed in the presentinvention is a step which leads to a significant increase in the contentof iso-paraffins. Specifically, it is preferred that the content (wt.-%)of iso-paraffins is increased by the isomerization step by at least 30percentage points, more preferably at least 50 percentage points,further preferably at least 60 percentage points, most preferably atleast 70 percentage points. To be specific, assuming that theiso-paraffin content of the hydrocarbon raw material (organic materialin the liquid component) is 1 wt.-%, then the iso-paraffin content ofthe intermediate product after isomerization is most preferably at least71 wt.-% (an increase of 70 percentage points).

An isomeric raw material obtained by an isomerization step as describedabove can be fed directly to the thermal cracking procedure. In otherwords, no purification is necessary after the isomerization step, sothat the efficiency of the process can be further improved.

Cracking Step

In the present invention, the thermal cracking in the cracking step isconducted at a temperature (coil outlet temperature COT) of at most 825°C. The COT is usually the highest temperature in the cracker. Atemperature of at most 825° C. allows producing the biohydrocarbonshaving a high propylene content. A higher temperature shifts the productdistribution and decreases the content of desired propylene. Preferably,the thermal cracking in the cracking step is conducted at a temperatureof at least 740° C., more preferably at least 760° C. Highest propyleneyields are achieved in the temperature range of 780−820° C., which istherefore preferable. On the other hand, even lower temperatures providehigh propylene yields, while the amount of un-reacted educts increases.Thus, when recycling the un-reacted products to the thermal cracking,very high overall yields of propylene can be achieved.

Hence, the thermal cracking in the cracking step may preferably beconducted at a temperature of at most 820° C., at most 810° C., at most800° C., further preferably at most 790° C., even further preferably atmost 780° C.

The thermal cracking preferably comprises steam cracking, since steamcracking facilities are widely used in petrochemistry and the processingconditions are well known, thus requiring only few modifications ofestablished processes. Thermal cracking is preferably carried outwithout catalyst. However, additives such as DMDS (dimethyl disulfide)may be used in the cracking step to reduce coke formation.

Steam cracking is preferably performed at a flow rate ratio betweenwater and the isomeric raw material (H₂O flow rate [kg/h]/iso-HC flowrate [kg/h]) of 0.01 to 5.00. Preferably, the flow rate ratio is atleast 0.05, preferably at least 0.10, more preferably at least 0.20,even more preferably at least 0.25. Preferably, the flow rate ratio isat most 3.00, preferably at most 1.50, more preferably at most 1.00,even more preferably at most 0.70, or at most 0.50. In the presentinvention, a medium range flow rate ratio, e.g. in the range of 0.25 to0.70, is favorable since it allows production of the desired productswith high yield.

In general, the pressure in the thermal cracking step is in the range of0.9 to 3.0 bar (absolute), preferably at least 1.0 bar, more preferableat least 1.1 bar or 1.2 bar, and preferably at most 2.5 bar, morepreferably 2.2 bar or 2.0 bar.

In the present invention, the biohydrocarbons produced by the method ofthe present invention preferably comprise at least 15 wt.-% propylene,since propylene is well suited for the production of petrochemical rawmaterials and in particular as a monomer or a monomer precursor inpolymer industry. The present invention provides a significantimprovement over conventional methods, not only from an environmentalaspect, but also in view of product distribution since the presentinvention may provide propylene yields which are even higher thanachieved by conventional methods. The biohydrocarbons preferablycomprise at least 16 wt.-%, preferably at least 17 wt.-%, morepreferably at least 18 wt.-%, at least 19 wt.-%, at least 20 wt.-%, orat least 21 wt.-% propylene.

As already said above, the products (biohydrocarbons) of the method ofthe present invention are particularly suitable as raw materials forconventional petrochemistry, and in particular polymer industry.Specifically, the products obtained from the present invention show aproduct distribution which is similar to, and even favorable over, theproduct distribution obtained from thermal (steam) cracking ofconventional (fossil) raw material. Thus, these products can be added tothe known value-added chain while no significant modifications ofproduction processes are required. In effect, it is thus possible toproduce polymers, especially polyolefins and/or PET, derived exclusivelyfrom bio-renewable material.

The present invention further provides a method of producing a polymerusing the method of producing biohydrocarbons of the present invention.The polymer production method optionally comprises a step of purifyingthe biohydrocarbons to provide biomonomers for polymerization. Themethod further optionally comprises a step of chemically modifying thebiohydrocarbons or a part thereof to provide biomonomers forpolymerization. The method comprises polymerizing at least a part of thebiomonomers to obtain a polymer. In the present invention, the polymeris preferably a polyethylene terephthalate (PET), a polyolefin, or aderivative thereof.

Further, the present invention provides a mixture of biohydrocarbonsobtainable by the method of the present invention. The mixture ofhydrocarbons corresponds to the mixture which is directly obtained afterthermal cracking without further purification. Accordingly, although theproduct distribution is similar to that of thermal cracking of fossilraw materials, the use of bio-renewable raw materials leaves afingerprint (mainly in the high molecular waste products, but also to aminor degree in the medium molecular weight products) so that adistinction from conventional products is possible, e.g. using GC×GCanalysis.

EXAMPLES

Laboratory scale experiments were carried out using the equipment shownin FIG. 1. In the apparatus of FIG. 1, hydrocarbons and water areprovided in reservoir 2 and 3, respectively. Mass flow is determinedusing an electronic balance 1. Water and hydrocarbons are pumped intoevaporators 7 via valves 6 using a water pump 5 and a peristaltic pump4, respectively. Evaporated materials are mixed in mixer 8 and fed tothe reactor 9 having sensors to determine temperatures T1 to T8. Coilinlet pressure (CIP) and coil outlet pressure (COP) are determined usingsensors (CIP, COP) at appropriate positions. Reaction products are inputinto a GC×GC-FID/TOF-MS 13 via heated sampling oven after having beenadmixed with an internal standard 10, the addition amount of which iscontrolled using a coriolis mass flow controller 11. Internal pressureof the reaction system is adjusted using the outlet pressure restrictionvalve 14. Further, water cooled heat exchanger 15, gas/liquid separator16, dehydrator 17, refinery gas analyzer 18, and condensate drum 19 areprovided to further analyze and recover the products.

Measurement of Isomerization Degree

The isomerization degree of the isomeric raw material is measured byGC×GC analysis as disclosed by Van Geem et. al., “On-line analysis ofcomplex hydrocarbon mixtures using comprehensive two-dimensional gaschromatography” in Journal of Chromatography A, 2010, vol. 1217, issue43, p. 6623-6633.

Specifically, comprehensive 2D gas chromatography (GC×GC) is used todetermine the detailed composition of the isomeric raw material. GC×GCdiffers from two-dimensional GC, since not only a few fractions of theeluent from the first column but the entire sample is separated on twodifferent columns. Compared to one-dimensional GC, GC×GC offers animproved resolution for all the components of interest, without loss oftime. The signal-to-noise ratio (and sensitivity) is also significantlyenhanced resulting in improved accuracy.

The GC×GC set-up is shown in the left part of FIG. 2. In FIG. 2, (S0)shows the general set-up of a dual-jet cryogenic modulator; in (S1) theright-hand-side jet traps eluent from 1^(st) dimension column; in (S2)cold spot heats up and analyte pulse into 2^(nd) dimensioncolumn+left-hand-side jet switch on; (S3) shows the next modulationcycle.

In detail, two distinctly different separation columns are used whichare based on two statistically independent separation mechanisms,so-called orthogonal separations. The first column contains a non-polarstationary phase (separation based on volatility), the second column ismuch shorter and narrower and contains a (medium) polar stationary phase(separation based on analyte-stationary phase interaction). Oneadvantage of orthogonal separation is that ordered structures forstructurally related components show up in the GC×GC chromatograms.Between the two columns an interface, a cryogenic modulator, is present(cf. right part of FIG. 2). Its main role is to trap adjacent fractionsof the analyte eluting from the first-dimension column by cryogeniccooling, and heating-up these cold spots rapidly to release them asrefocused analyte pulses into the second-dimension column. To preventleakage of the first column material, two jets are used that each inturn collect the 1^(st) dimension eluent.

The second-dimension separation must be completed before the nextfraction is injected to avoid wrap-around. Wrap-around occurs whensecond-dimension peaks show up in a later modulation than in which theywere injected. This explains the shorter and narrower second-dimensioncolumn as compared to the first one.

The most common ways of visualization of the GC×GC chromatograms are a2D color or grayscale plot, a contour plot and a 3D plot, see FIG. 3.Two dimensional chromatograms can be obtained because thesecond-dimension separation time equals the modulation time.

In order to maintain the separation obtained in the first-dimensioncolumn, the narrow fractions trapped by the modulator and released inthe 2^(nd) column should be no wider than one quarter of the peak widthsin the 1^(st) dimension. The term “comprehensive” refers to this aspectof comprehensive GC×GC. As a consequence of this characteristic andsince the modulation time must equal the 2^(nd) dimension run time,second-dimension separations should be very fast, in the order of 2 to 8seconds. This will render very narrow 2^(nd) dimension peaks and ademand of correspondingly fast detectors, like an FID (flame ionizationdetector) for quantitative analysis or a TOF-MS (time-of-flight massspectrometer) for qualitative analysis.

A quantitative analysis of a sample is carried out with the use of aGC×GC-FID. This analysis is based on the peak volumes. The peak volumein a chromatogram is proportional to the quantity of the correspondingcomponent. Hence, Integration of the peaks observed in the chromatogrammakes it possible to obtain a quantitative analysis of the sample.

A detailed qualitative sample characterization is obtained usinginformation from the sample's GC×GC-TOF-MS spectrum, the molecularlibrary and the Kovats retention indices. Operation of the GC×GC-TOF-MSis computer controlled, with GC peaks automatically detected as theyemerge from the column. Each individual mass spectrum is directlyrecorded onto the hard disk for subsequent analysis. This techniqueprovides information on the identity of every individual componentobtained by chromatographic separation by taking advantage of the commonfragmentation pathways for individual substance classes. Theinterpretation of the mass spectra and library search using e.g. theXCalibur software allows the identification of various peaks observed inthe chromatogram.

In the Examples, the data obtained with TOF-MS was acquired using ThermoScientific's Xcalibur software. The raw GC×GC data files were processedusing HyperChrom, i.e. the Chrom-Card extension for GC×GC data handlingthat enables 3D representation as well as the common color plotrepresentation of the data. HyperChrom also allows automatic 3D peakquantification and identification. The latter is accomplished by crossreferencing the measured mass spectra to the spectra in the available MSlibraries.

Concerning the off-line GC×GC analysis of complex hydrocarbon mixtures,each peak is assigned a unique name, or is classed into a certain groupof components, based on the ordered retention of components and MSconfirmation. Only components with identical molecular mass are possiblygrouped. To each (grouped) component a weight fraction was assigned byinternal normalization:

$x_{i} = \frac{f_{i} \cdot V_{i}}{\sum\limits_{i = 1}^{n}{f_{i} \cdot V_{i}}}$

where f_(i) is the relative response factor for component i, used tocorrect the corresponding total peak volume V_(i) obtained with FID. Ithas been demonstrated that various isomeric hydrocarbons, produce onlyslightly different relative FID responses, so that a fair approximationof the relative response factor may be written as:

$f_{i} = {\frac{M_{i}}{N_{C,i}} \cdot \frac{1}{M_{{CH}_{4}}}}$

where M_(i) is the molecular mass of component i with N_(C,i) carbonatoms.

Effluent Analysis

Effluent analysis of the cracking product is performed using theprocedure described by Pyl et. al. (Pyl, S. P.; Schietekat, C. M.; VanGeem, K. M.; Reyniers, M.-F.; Vercammen, J.; Beens, J.; Marin, G. B.,Rapeseed oil methyl ester pyrolysis: On-line product analysis usingcomprehensive two-dimensional gas chromatography. J. Chromatogr. A 2011,1218, (21), 3217-3223).

Specifically, the quantification of the reactor effluent is done usingan external standard (N₂) which is added to the reactor effluent in thesampling oven. In order to combine the data of the various instruments,having both TCD and FID detectors, multiple reference components wereused. This is schematically presented in FIG. 4.

The fraction of the reactor effluent containing the permanent gasses andthe C4-hydrocarbons is injected on the refinery gas analyzer (RGA). N₂,H₂, CO, CO₂, CH₂, ethane, ethene and acetylene are detected with a TCD.The mass flow rate of these species, dm_(i)/dt, can be determined basedon the known mass flow rate of N₂ using the following equation whereA_(i) represents the surface area obtained by the detector. The responsefactor for each C4-species, f_(i), was determined using a calibrationmixture provided by Air Liquide, Belgium.

${\overset{.}{m}}_{i} = {\frac{f_{i}A_{i}}{f_{N_{2}}A_{N_{2}}}{\overset{.}{m}}_{N_{2}}}$

A FID detector on the RGA analyzes C1 to C4 hydrocarbons. Methane,detected on the TCD detector, acts as a secondary internal standard inorder to quantify the other detected molecules using the followingequation:

${\overset{.}{m}}_{i} = {\frac{f_{i}A_{i}}{f_{{CH}_{4}}A_{{CH}_{4}}}{\overset{.}{m}}_{{CH}_{4}}}$

Settings of the RGA are shown in Table 1.

The GC×GC-FID allows quantification of the entire effluent stream, asidefrom N₂, H₂, CO, CO₂ and H₂O. Methane was used as secondary internalstandard. The mass flow rates of the detected species were calculatedusing the above equation, response factors were calculated using theeffective carbon number method. Settings of the GC×GC are shown in Table2.

TABLE 1 (refinery gas analyzer settings): RGA channel 1 channel 2channel 3 Detector FID, 200° C. TCD, 160° C. TCD, 160° C. Injection(gas) 50 μl, 80° C. 230 μl, 80° C. 250 μl, 80° C. Carrier gas He He N₂Column Pre Rtx-1^(a) Hayesep Q Hayesep T Analytical Rt-Al BOND^(b)Hayesep N Carbosphere Molsieve 5A Oven temperature 50 → 120° C. 80° C.80° C. (5° C./min) ^(a)dimethyl polysiloxane (Restek);^(b)divinylbenzene ethylene glycol/dimethylacrylate (Restek), ^(c) 100%divinylbenzene (Restek)

TABLE 2 (GC × GC settings): GC × GC Detectors FID, 300° C. TOF-MS,35-400 amu Injection Off-line 0.2 μl, split flow 150 ml/min, 300° C.On-line 250 μl (gas), split flow 20 ml/min, 300° C. Carrier gas HeColumn First Rtx-1 PONA^(a) Second BPX-50^(b) Oven Off-line 40° C. → 250° C. (3° C./min) temperature On-line −40° C. (4 min hold) → 40° C. (5°C./min) → 300° C. (4° C./min) Modulation 5 s Period ^(a)dimethylpolysiloxane (Restek); ^(b)50% phenyl polysilphenylene-siloxane (SGE)

Raw Material Composition C1:

A mixture (isomeric raw material) comprising 89 wt.-% iso-alkanes(i-paraffins) and 11 wt.-% n-alkanes (n-paraffins) is provided. Theaverage molecular weight is 227 g/mol. The composition of the mixture isanalyzed by GC×GC analysis and the results are shown in Table 3. Thecomposition corresponds to a hydrocarbon composition (diesel fraction)derived from a bio-renewable feedstock which is subjected tohydrotreating and isomerization.

Raw Material Composition C2 (Comparative):

This mixture comprises about 49 wt.-% iso-alkanes and 51 wt.-%n-alkanes. The average molecular weight is 230 g/mol. The composition ofthe mixture is analyzed by GC-GC analysis and the results are shown inTable 3.

The composition corresponds to a hydrocarbon composition (dieselfraction) derived from a bio-renewable feedstock which is subjected tohydrotreating isomerization, but to a lower degree than in compositionC1.

TABLE 3 C1 C2 Carbon number i-paraffins n-paraffins i-paraffinsn-paraffins C5 0.01 0.01 0 0 C6 0.07 0.01 0 0.01 C7 0.08 0.05 0.19 0.08C8 0.24 0.13 0.24 0.12 C9 0.65 0.22 0.29 0.14 C10 1.02 0.22 0.36 0.14C11 1.15 0.19 0.41 0.15 C12 1.23 0.18 0.48 0.21 C13 1.42 0.19 0.53 0.29C14 2.06 0.36 1.06 0.6 C15 9.46 1.56 6.53 6.92 C16 19.35 2.34 13.6216.41 C17 20.95 2.47 9.87 7.89 C18 29.93 2.78 14.35 17.88 C19 0.62 0.050.28 0.11 C20 0.58 0 0.2 0.18 C21 0.1 0.02 0.05 0.02 C22 0.11 0.01 0.050.03 C23 0.04 0.01 0.04 0.02 C24 0.04 0 0.03 0.03 C25 0 0 0.01 0 C26 0 00.04 0 Sum 89.11 wt % 10.80 wt % 48.63 wt % 51.23 wt %

Example 1

Steam cracking was carried out in laboratory scale using raw materialcomposition C1 at a temperature (coil outlet temperature, COT) of 780°C. and a dilution of 0.5 (flow rate ratio of water to raw materialcomposition C1; water [kg/h]/C1 [kg/h]) at 1.7 bar (absolute) in a 1.475m long tubular reactor made of Incoloy 800HT steel (30-35 wt.-% Ni,19-23 wt.-% CR, >39.5 wt.-% Fe) having an inner diameter of 6 mm. Theraw material composition flow rate was fixed at 150 g/h. The coil outlettemperature (COT) was measured at a position 1.24 m downstream the inletof the reactor, which corresponds to the region having the highesttemperature in the reactor.

The product mixture (biohydrocarbons) was analyzed by GC×GC, asmentioned above. The results are shown in Table 4.

Examples 2 to 10 and Comparative Examples 11 to 20

Steam cracking was carried out similar to Example 1, except for changingraw material composition, COT and dilution, as indicated in Tables 4 and5. The product mixtures were analyzed by GC×GC, and the results areshown in Tables 4 and 5.

TABLE 4 Example # 1 2 3 4 5 6 7 8 9 10 Raw Mat. C1 C1 C1 C1 C1 C1 C1 C1C1 C1 COT (° C.) 780 800 820 840 860 780 800 820 840 860 H₂O g/h 75 7575 75 75 52 52 52 52 52 Dilution 0.5 0.5 0.5 0.5 0.5 0.35 0.35 0.35 0.350.35 Methane 8.17 9.71 10.48 11.11 12.25 9.14 9.65 10.31 10.79 13.45Ethene 31.22 32.46 32.98 33.57 33.74 29.35 31.67 32.17 33.15 33.32Propene 23.06 23.10 20.47 18.16 13.97 21.85 21.71 18.99 16.28 13.39Butene 10.29 9.44 10.18 7.24 3.39 13.28 12.14 9.30 5.65 2.20 Butadiene5.27 6.13 6.17 5.80 4.44 5.02 5.52 5.31 4.23 3.94 C5 5.61 5.41 4.38 3.802.52 5.71 5.11 4.43 3.40 3.02 Benzene 2.09 3.31 5.03 6.59 8.26 3.29 4.147.00 7.85 9.19 C7 1.50 1.76 2.21 2.52 2.76 2.06 2.07 2.74 2.95 3.21 C80.50 0.52 0.77 1.06 1.67 0.70 0.68 1.14 1.43 1.78 others 12.28 8.15 7.3410.16 17.00 9.60 7.32 8.61 14.27 16.50 BTX total 3.25 4.96 7.34 9.2511.27 5.19 6.34 9.88 11.03 12.63 unconverted 2.08 0.00 0.00 0.00 0.001.12 0.00 0.00 0.00 0.00

TABLE 5 Comparative Example # 11 12 13 14 15 16 17 18 19 20 Raw Mat. C2C2 C2 C2 C2 C2 C2 C2 C2 C2 COT (° C.) 780 800 820 840 860 780 800 820840 860 H₂O g/h 75 75 75 75 75 52 52 52 52 52 Dilution 0.5 0.5 0.5 0.50.5 0.35 0.35 0.35 0.35 0.35 Methane 7.00 8.65 10.19 11.96 12.86 8.4610.32 11.15 14.36 15.00 Ethene 31.95 35.67 37.34 39.04 39.55 32.57 35.0336.25 38.14 39.46 Propene 20.22 21.34 19.82 17.66 14.71 21.15 20.9218.98 15.93 13.38 Butene 8.00 6.97 4.94 3.00 1.98 7.48 6.48 4.12 2.271.96 Butadiene 4.75 5.82 5.91 5.42 4.69 5.12 5.47 5.32 4.76 4.21 C5 5.794.76 3.92 2.92 2.86 5.89 3.27 3.85 2.49 2.46 Benzene 1.81 3.13 4.57 6.097.84 3.22 4.44 5.79 7.45 8.65 C7 1.48 1.28 1.44 1.78 2.13 1.77 1.65 1.932.23 2.44 C8 2.42 0.89 0.88 1.01 1.29 1.13 0.84 0.98 1.26 1.37 others16.59 11.50 10.99 11.12 12.09 13.21 11.57 11.64 11.12 11.07 BTX total2.68 4.38 6.18 8.07 10.22 4.76 6.30 7.95 9.96 11.43 unconverted 6.751.14 0.40 0.12 0.00 1.54 0.11 0.10 0.00 0.00

As can be seen from the above results, a high degree of desirable BTXproducts (i.e. benzene, toluene, xylenes) can be produced attemperatures of 780° C. or more, in particular 800° C. or more.Surprisingly, high isomerization of the raw material composition resultsin increased amount of BTX products and also in higher overallconversion rates (lower amount of unconverted products) even in theintermediate temperature range of 800-840° C.

1. A method for producing biohydrocarbons, the method comprising: providing an isomeric raw material obtained from a bio-renewable feedstock and containing at least 65 wt.-% iso-paraffins; and thermally cracking the isomeric raw material to produce biohydrocarbons, wherein the thermal cracking is conducted at a coil outlet temperature (COT) of at most 825° C.
 2. The method according to claim 1, wherein the isomeric raw material contains at least 68 wt.-%, preferably at least 70 wt.-%, more preferably at least 75 wt.-%, more preferably at least 80 wt.-%, more preferably at least 85 wt.-%, more preferably at least 90 wt.-% iso-paraffins.
 3. The method according to claim 1, wherein the thermal cracking is conducted at a coil outlet temperature (COT) of at most 820° C., preferably at most 810° C., preferably at most 800° C., at most 790° C., or at most 780° C.
 4. The method according to claim 1, wherein the thermal cracking is conducted at a coil outlet temperature (COT) of at least 700° C., preferably at least 720° C., at least 740° C., at least 750° C., or at least 760° C.
 5. The method for producing biohydrocarbons according to claim 1, wherein providing of the isomeric raw material comprises: preparing a hydrocarbon raw material from the bio-renewable feedstock; and optionally subjecting at least straight chain hydrocarbons in the hydrocarbon raw material to an isomerization treatment to prepare the isomeric raw material.
 6. The method according to claim 5, wherein the preparing comprises: deoxygenating the bio-renewable feedstock, wherein deoxygenating the bio-renewable feedstock is a hydrotreatment step, preferably a hydrodeoxygenation step.
 7. The method according to claim 5, wherein the preparing comprises: hydrocracking hydrocarbons in the hydrocarbon raw material.
 8. The method according to claim 1, wherein the isomeric raw material contains at least one of a diesel range fraction and a naphtha range fraction and at least the diesel range fraction and/or the naphtha range fraction is subjected to thermal cracking.
 9. The method according to claim 1, wherein the isomeric raw material is selected from one of Fractions A and B, wherein: Fraction A contains more than 50 wt.-%, preferably 75 wt.-% or more, more preferably 90 wt.-% or more of C10-C20 hydrocarbons, a content of even-numbered hydrocarbons in the C10-C20 range being preferably more than 50 wt.-%, and the fraction A containing 1.0 wt.-% or less, preferably 0.5 wt.-% or less, more preferably 0.2 wt.-% or less aromatics, and less than 2.0, preferably 1.0 wt.-% or less, more preferably 0.5 wt.-% or less of olefins; and Fraction B contains more than 50 wt.-%, preferably 75 wt.-% or more, more preferably 90 wt.-% or more of C5-C10 hydrocarbons, and the fraction B containing 1.0 wt.-% or less, preferably 0.5 wt.-% or less, more preferably 0.2 wt.-% or less aromatics, and less than 2.0, preferably 1.0 wt.-% or less, more preferably 0.5 wt.-% or less of olefins.
 10. The method according to claim 1, wherein the thermal cracking comprises: steam cracking; and wherein the steam cracking is performed at a flow rate ratio between water and the isomeric raw material (H₂O flow rate [kg/h]/iso-HC flow rate [kg/h]) of 0.05 to 1.20; and wherein the flow rate ratio between water and the isomeric raw material is preferably at least 0.10, further preferably at least 0.20, more preferably at least 0.25, or at least 0.30, and wherein the flow rate ratio between water and the isomeric raw material is preferably at most 1.00, further preferably at most 0.80, more preferably at most 0.70, at most 0.60, or at most 0.50.
 11. The method according to claim 1, wherein the biohydrocarbons contain at least 15 wt.-%, preferably at least 16 wt.-%, preferably at least 17 wt.-%, preferably at least 18 wt.-%, preferably at least 19 wt.-%, at least 20 wt.-%, or at least 21 wt.-% propene.
 12. A method of producing a polymer, comprising: producing biohydrocarbons according to the method of claim 1; optionally purifying and/or chemically modifying at least a part of the biohydrocarbons to provide biomonomers; and polymerizing the biomonomers to obtain a polymer.
 13. The method according to claim 12, wherein the polymer is a polyolefin, such as polypropylene and polyethylene, or a copolymer containing propylene units and/or polyethylene units, such as polyethylene terephthalate, or a derivative thereof; and/or wherein the method employs at least 50 wt.-%, preferably at least 80 wt.-%, more preferably at least 90 wt.-%, more preferably at least 95 wt.-%, more preferably more than 99 wt.-%, even more preferably 100 wt.-% of monomers derived from bio-renewable raw materials, relative to all monomers constituting the polymer.
 14. The method according to claim 12, comprising: forming an article, such as a film, beads, or a molded article from the polymer.
 15. A mixture of biohydrocarbons obtainable by a method comprising: providing an isomeric raw material obtained from a bio-renewable feedstock and containing at least 65 wt.-% iso-paraffins; and thermally cracking the isomeric raw material to produce biohydrocarbons, wherein the thermal cracking is conducted at a coil outlet temperature (COT) of at most 825° C. 